Method for producing hydrocarbons in an in situ combustion operation



K. C. TEN BRINK METHOD FOR PRODUCING HYDROCARBONS IN AN IN Dec. 19, 1961SITU COMBUSTION OPERATION Filed June 1l, 1958 3 013,609 METHGD FORPRODCNG HYDRGCARBGNS 1N AN IN SITU CGMBUSTIQN PERATION Karl C. TenBrink, Houston, Tex., assigner to Texaco Inc., a corporation of DelawareFiled June 11, 1953, Ser. No. 741,341 3 Claims. (Cl. 16o-69) Thisinvention relates to the production of hydrocarbons fromhydrocarbon-containing formations. vMore particularly, this inventionrelates to a method of carrying out an in situ combustion operation forthe production and recovery of hydrocarbons from a hydrocarboncontainingformation, such as a petroleum producing formation, tar sands, oilshales and the like. In accordance with one specific embodiment thisinvention is directed to a well completion assembly particularly usefulin the production of hydrocarbons from underground formations by amethod involving in situ combustion.

Various techniques have been proposed for the recovery of hydrocarbonsfrom underground formations and for the treatment ofhydrocarbon-containing formations. For example, for the recovery ofpetroleum from petroleum producing formations secondary reco-veryoperations which involve water flooding or thermal recovery methods suchas in situ combustion, employing at least one injection well and atleast one production well, have been proposed. As indicated hereinabove,the practice of this invention is particularly directed to thermalrecovery methods such as methods involving in situ combustion for theproduction of petroleum and the like from underground formations.

Explanatory of an in situ com-bustion operation and indicative as to howan in situ co-mbustion operation may be carried out, a high temperaturezone is established in an underground hydrocarbon orpetroleum-containing formation in the vicinity of a wellborepenetratinggthe same. Suitable means for establishing or creating a hightemperature zone within the wellbore penetrating ahydrocarbon-containing formation may comprise an electric heating deviceor a gas fired bottom hole igniter or heater. A suitable device forinitiating in situ combustion and for establishing a high temperaturezoneA within a wellbore is described in U.S. 2,722,278. Upon introducinga combustion-supporting gas, such as air, into the thus-heated wellboreadjacent the petroleum-containing `formation a resulting hightemperature combustion zone is generated therein by the reaction betweenthe oxygen and the combustible petroleum hydrocarbons or residues withinthe formation, such as combustible residues resulting from thedistillation and/or thermal cracking of the petroleum hydrocarbonsoriginally in place or introduced thereinto. This high temperaturecombustion zone (temperature in the range 700-2000 F., more or less)will commence to move into the formation outwardly from the wellboreupon continued introduction of air into the wellbore. Leaving this hightemperature zone is a relatively high temperature gas stream which, asit moves outwardly into the formation, loses heat to the formaftion. Bythis method the high temperature combustion zone or flame front is movedfor a considerable distance, for example a distance in the range 3-25',more or less, outwardly from the wellbore into the formation withoutfurther direct application of heat to the zone of the formation adjacentthe wellbore. Continued direct application of heat to this zone,however, may sometimes be desir. able. The distance which the hightemperature combustion zone moves radially outwardly, and as a resultthe volume of the petroleum-containing formation swept by 3,013,609Patented Dec. 19, 1 961 rate of heat generation (combustion ofcombustible residues) and the rate of heat loss to the surroundingformation.

It has been postulated that the following mechanisms are important inthe movement of the high temperature combustion zone outwardly from awellbore into the petroleum producing formation during an in situcombustion operation therein. Although the exact mechanism of an in situcombustion is not definitely and completely known, the followingsequence of events are postulated and are presented herein for thepurpose of enabling one skilled in the art to better understand thisinvention.

As the high temperature combustion zone approaches any given volume ofthe hydrocarbon or petroleum-containing formation the temperature ofthis volume of formation rises. This results, first, in a reduction inthe viscosity of the formation fluids therein (oil, water) due totemperature increase. These fluids may then be moved more readily underthe influence of the hot combustion gas stream continuously emanatingfrom the high temperature combustion zone. As the temperature continuesto rise, distillations of the formation fluids begin. The products ofthese distillations condense in cooler regions of the formation removedfrom the high temperature combustion zone in the direction of liow ofthe hot combustion gases therein. The distillations continue as thetemperature rises within the given portion of the formation until theheavier components remaining from the hydrocarbons or petroleumoriginally in place within the formation or introduced thereinto priorto initiating in situ combustion therein begin to crack and yieldhydro-A combustion-supporting gas increases due to depletion ofcombustible residues in the preceding regions of the formation, a pointwill be reached at which the coke or other `combustible residues willbegin to react with the oxygen with the resulting release of heat to theformation and the combustion gas stream emanating therefrom. This heatis carried away by the on-moving combustion gas stream and also to someextent by thermal conduction to adjoining regions of the formation. Whenthe coke or combustible residue has been burned away there remains avolume of liquid-freeformation.

Another method of carrying out an in situ-combustion operation involvingoperations as ldisclosed hereinabove, I'

i.e., initiation of a high temperature zone within a wellbore and thencausing an in situ combustion zone to move outwardly therefrom into theformation toward a production well, is known. In this method after thehigh temperature combustion zone has moved a suflicient distanceoutwardly from the wellbore, such as a distance in the range 5-50, airor other combustion-supporting l gas is injected into another `wellremoved from the well wherein in situ combustion was initiated. Whenthese operations are carried out the in situ combustion zone or flamefront moves countercurrently with respect to the flow ofthecombustion-supporting gas (air) within thev formation 'undergoingtreatment, i.e., the in situ combustion zoneinoves toward the other wellinto which the combustion-'supporting gas is injected while the combusftion-supporting gas as well as thel resulting hotrcombus- .tion gasesand displacedhydrocarbons, partiallynoxygenl ated hydrocarbons, etc.,mojvefrorn this other well ytoward the wel1 wherein in situ, combustionwas initiated.v `Theg mechanisms-and technique for carrying out an insitu f. I combustion operation in accordance with thismethod j arecompletely disclosedv in U.S. 2,793,696; The dis- As the temperaturecon-` closures of this patent are herein incorporated and made part ofthis disclosure.

In an in situ combustion operation many difficulties arise in theproduction well, i.e., the well wherein the formation fluids displacedin the in situ combustion operation are recovered and produced. Thesewells in an in situ combustion operation are subjected to rather hightemperature, above about 800 F. Under the high ternperature conditionsexperienced in an in situ combustion operation these wells are subjectto failure due to tubing, liner or casing collapse brought on by thehigh temperatures in the wells. Additionally well fires sometimes occurtherein. These Well fires arise due to the intermingling within the wellof the produced hydrocarbons or partially oxygenated hydrocarbons withan oxidizing or oxygen-containing gas such as air. Further, in someinstances the high temperatures experienced in an in situ combustionoperation sometimes cause collapse of the wellbore itself, if thewellbore is unsupported, duc to the well fires or explosions within thewellbore.

Accordingly, it is an object of this invention to provide an improved insitu combustion operation for the production of hydrocarbons orpartially oxygenated hydrocarbons from hydrocarbon-containing formationssuch as petroleum formations, tar sands, oil shales and the like.

Another object of this invention is to provide a method for carrying outan in situ combustion operation wherein the production well, i.e., thewell wherein the resulting displaced formation uids are produced, isprotected against the high temperatures experienced in an in situcombustion operation.

Yet another object of this invention is to provide a method for theelimination of well fires in a production well involved -in an in situcombustion operation.

Yet another object of this invention is to provide a method for theprotection of the well and/or equipment of a production well involved inan in situ combustion operation.

Still another object of this invention is to provide a method `for thecreation of a substantially non-oxidizing environment in the wellbore ofa production well involved in an in situ combustion operation.

How these and other objects of this invention are accomplished willbecome apparent in the light of the accompanying disclosure and drawingwhich schematically illustrates one embodiment of the practice of thisnvention particularly directed to a method of operating a product-ionwell involved in an in situ combustion operation. In at least oneembodiment of the practice of this invention at least one of theforegoing objects will be achieved.

In an in situ combustion operation wherein a well bore penetrates ahydrocarbon-containing formation which is undergoing in situ combustionand wherein formation fluids are displaced during the in situ combustionoperation and are produced via the well bore, improved operation isobtained by cooling the wellbore adjacent the formation undergoing insitu combustion. The resulting produced formation fluids, gaseoushydrocarbons, liquid hydrocarbons, partially oxygenated hydrocarbons andcombustion gases are cooled as they enter the well bore. Within the wellbore the thus-produced liquids are collected at a location or sumptherein relatively remote from that portion of the wellbore adjacent theformation undergoing in situ combustion and are recovered therefrom atthe surface. Desirably suitable pumping means are located within thewellbore wherein the thus-produced liquids are collected as means formoving these liquids to the surface.

In the practice of this invention, particularly with respect to oneembodiment thereofas illustrated in the accornpanying drawing, awellbore 11 is shown penetrating a hydrocarbon-containing formation 12.As illustrated in the drawing the wellbore 11 extends through thehydrocarbon-containing formation 12 into an underlying formation 14,which may be the lower portion of formation 12., wherein the wellbore isbottomed. The wellbore 11, particularly that portion penetratinghydrocarbon-containing formation 12, is shown lined with cement 15.Also, as illustrated the wellbore is provided with a casing 16 extendingthrough the hydrocarboncontaining formation 12 into the underlyingformation 14. The casing, cement and formation are perforated at 1S toprovide for the entry of the formation fluids displaced during the insitu combustion operation from the hydrocarbon-containing formation 12into the interior of casing 16.

Within casing 16 is positioned a heat exchanger or cooler 19, such as atwo-pass heat exchanger, which is provided with a conduit 20 for thesupply of liquid coolant such as Water or formation brine and the like.The heat exchanger or cooler 19 is positioned within wellbore 11adjacent the hydrocarbon-containing formation which is undergoing insitu combustion and located therein so as to cool or maintain thewellbore temperature at a relatively low level during the in situcombustion operation. Extending through well bore 11, and preferablythrough heat exchanger 19, as shown, is production tubing 21. Productiontubing 21 is shown concentrically positioned within wellbore 11 and withreespect to heat exchanger 19. As illustrated production tubing 21extends below heat exchanger 19 into the lower end of wellbore 11. Thislower end of wellbore 11 serves as a sump for the collection of theformation liquids, such as liquid hydrocarbons, partially oxygenatedhydrocarbons, water, ete., displaced into wellbore 11 during the in situcombustion operation.

Associated with production tubing 21 is a well pump 22 adapted towithdraw formation liquids which collect in the lower end of wellbore 11and to pump the same via production tubing 21 for recovery at thesurface through conduit 24. As illustrated, pump 22 is actuated by meansof sucker rod 25 operatively connected at the upper end thereof to asuitable lifting or pumping means, not illustrated. As illustrated inthe drawing, heat exchanger 19 is provided with spray nozzles 26 forspraying into the wellbore 11 the liquid coolant which is supplied viaconduit 20 into heat exchanger 19 which is employed to cool the wellboreand the resulting produc-ed formation fluids by indirect heat exchange.

In the practice of this invention as illustrated in the accompanyingdrawing formation fiuids, including liquid hydrocarbons, partiallyoxygenated hydrocarbons as well as gaseous hydrocarbons and gaseousproducts of comhustion such as carbon dioxide, carbon monoxide, steam invarying amounts, are produced or displaced from thehydrocarbon-containing formation 12 during the in situ combustionoperation as these formation fluids enter wellbore 11 via perforations18. As the relatively hot formation `fluids enter wellbore 11 they arecooled by indirect heat exchange with the liquid coolant flowing withinheat exchanger 19 positioned within wellbore 11 immediately adjacent theformation 12 undergoing in situ combustion. Due to the close proximityof the heat exchanger 19 to the wellbore 11 and casing 16 and productiontubing 21 these elements are effectively protected against'unduly hightemperatures during the in situv combustion operation, particularly asthe high temperature combustion zone approaches wellbore 11.Accordingly, equipment failure such as casing collapse and tubingcollapse and wellbore disruption is inhibited or avoided. As theformation fluids enter the wellbore 11 via perforations 18 they arecooled by cooler 19. Certain of the components will condense and collectin the lower end of wellbore 11 together with the produced formationliquids. The produced gases and vaporous formation fiuids lwithinwellbore 11 are withdrawn from wellbore 11 at the surface throughsuitable means such as conduit 28. The formation liquids whichaccumulate in the bottom of wellbore 11 are pumped therefrom by means ofwell pump 22 which is operated through sucker rod 25 and recovered atthc surface via conduit 24.

`In accordance with a specific feature of this invention in addition tothe cooling of the wcllbore and associated well equipment adjacent theformation undergoing in situ combustion by indirect heat exchange withcooler 19, the wellbore and associated equipment therein are effectivelycooled by direct contact with the liquid coolant introduced into heatexchanger 19 via line 2t). In accordance with this embodiment instead ofreturning the coolant, such as water, from cooler 19 back to the surface(by means not shown) the liquid coolant is forced through spray nozzles26 associated with cooler 19 with the result that a liquid spray ofcoolant is forced into the wellbore 11 in the vicinity of the formationundergoing in situ combustion. This spray of liquid coolant by directcontact serves very effectively to cool the Wellbore and associatedequipment therein. Additionally vaporization of the coolant provides ashielding, non-oxidizing atmosphere within the wellbore with the resultthat wellbore fires and explosions are avoided.

Any suitable coolant, liquid or non-combustible gas, may be effectivelyemployed in the practice of this invention. Suitable coolants, inaddition to water, include aqueous brines such as formation brines.Aqueous brines and the like are less desirable, however, since brinestend to deposit salt Within the Wellbore. Iin some instances theresulting produced formation uids such as liquid hydrocarbons and thelike might be employed as the liquid coolant. ln those instances whereformation vfluids are employed as coolants it Iwould be more desirableto return the formation fluids to the surface rather than spraying themwithin the wellbore.

As illustrated in the drawing, the pump Z2 is shown positioned in thelower end of wellbore 11, below formation 12. By thus positioning thepump 22 at a location in the Wellbore relatively remote from thatportion of formation 12 undergoing in situ combustion the well pump isless likely to be exposed to unduly high temperatures during the in situcombustion operation. lf desired, however, well pump 22 may bepositioned within or in close heat exchange relationship with cooler .19so that cooler 19 effectively protects the well pump from hightemperatures.

Although in the practice of this invention, as illustrated in thedrawing, the wellbore 11 is shown lined with cement and provided with acasing, and perforated, an uncased or open wellbore might also beernployed. 'In such a situation the produced formation uids enterdirectly the wellbore from the formation.

As will be apparent to those skilled in the art many modifications andimprovements which do not depart from the spirit or scope of thisinvention will present themselves -to those skilled in the art in thelight of this disclosure.

Iclaim:

1. A method of producing hydrocarbons from a subsurfacehydrocarbon-containing formation including the steps: (l) initiating insitu combustion Within said formation to heat the formation uidstherein, (2) displacing the resulting heated formation fluids, includingliquid hydrocarbons, during the in situ combustion operation from thezone of in situ combustion toward the well bore of a production wellpenetrating said formation, (3) cooling by indirect heat exchange with arelatively cool liquid the resulting relatively hot `formation fluids asthey enter said well bore at a location adjacent said formationundergoing in situ combustion and by direct heat exchange by sprayingcoolant into contact with said well bore adjacent said formation to theextent nee'- essary to avoid equipment failure and Wellbore disrup` tiondue to high temperature conditions experienced as a result of said insitu combustion, (4) collecting the resulting cooled formation fluidswithin said wellbore at a location therein remote from said formation,and (5) transferring the resulting cooled formation fluids from the lastmentioned location via said wellbore to the surface.

2. A method of producing hydrocarbons from a subsurfacehydrocarbon-containing formation which comprises subjecting saidformation to an in situ combustion operation to displace saidhydrocarbons from said formation toward a production well penetratingsaid formation, cooling the thus-displaced hydrocarbons leaving saidformation as the displaced hydrocarbons enter the well bore of saidproduction well adjacent said formation to coo-l the thus-displacedhydrocarbons therein to the extent necessary to prevent casing andtubing collapse and Wellbore disruption due to fire, explosion and otherhigh temperature conditions as a result of said in situ combustion,collecting the thus-displaced hydrocarbons within said wellbore at alocation therein relatively remote from said formation, and producingthe resulting cooled hydrocarbons from said location, said cooling ofthe displaced hydrocarbons being accomplished by passing an aqueousliquid in indirect heat exchange with said displaced hydrocarbons and byspraying said aqueous liquid within said well bore adjacent saidformation undergoing in situ combustion for direct heat exchange.

3. A method of producing formation hydrocarbons from a subsurfacehydrocarbon-containing formation which comprises subjecting saidfor-mation to an in situ combustion operation to displace formationhydrocarbons within said formation toward a production well penetratingsaid formation, the Wellbore of-said well adjacent said producingformation being subjected to a relatively high temperature due to theaforesaid in situ combustion operation, cooling said wellbore adjacentsaid formation to maintain said wellbore relatively cool with respect tothe in situ combustion operation being carried out Within said formationby indirect heat exchange with a liquid coolant flowing through saidwell and by direct heat exchange by spraying liquid coolant into contactwith said well lbore adjacent said formation, and to the extentnecessary to inhibit wellbore equipment failure and disruption due tohigh temperature conditions experienced in said wellbore as a result ofsaid in situ combustion operation within said formation, collecting thedisplaced cooled hydrocarbons as they enter the wellbore from theformation undergoing in situ combustion, the resulting cooledhydrocarbons beingcollectedwithin said Wellbore at a location thereinrelatively remote from said formation, and producing the thus-collectedhydrocarbons from said location of said wellborev References Cited inthe le of this patent UNITED STATES PATENTS 1,263,618 Squires Apr. 23,1918 2,349,536 Bancroft May 23, 1944 2,444,756 Steffen July 6, 19482,584,606 Merriam et al. Feb. 5, 1952 2,734,579 IElkins Feb. 14, 1956(Page B-4l relied

1. A METHOD OF PRODUCING HYDROCARBONS FROM A SUBSURFACEHYDROCARBON-CONTAINING FORMATION INCLUDING THE STEPS: (1) INITIATING INSITU COMBUSTION WITHIN SAID FORMATION TO HEAT THE FORMATION FLUIDSTHEREIN, (2) DISPLACING THE RESULTING HEATED FORMATION FLUIDS, INCLUDINGLIQUID HYDROCARBONS, DURING THE IN SITU COMBUSTION OPERATION FROM THEZONE OF IN SITU COMBUSTION TOWARD THE WELL BORE OF A PRODUCTION WELLPENETRATING SAID FORMATION, (3) COOLING BY INDIRECT HEAT EXCHANGE WITH ARELATIVELY COOL LIQUID THE RESULTING RELATIVELY HOT FORMATION FLUIDS ASTHEY ENTER SAID WELL BORE AT A LOCATION ADJACENT SAID FORMATIONUNDERGOING IN SITU COMBUSTION AND BY DIRECT HEAT EXCHANGE BY SPRAYINGCOOLANT INTO CONTACT WITH SAID WELL BORE ADJACENT SAID FORMATION TO THEEXTENT NECESSARY TO AVOID EQUIPMENT FAILURE AND WELLBORE DISRUPTION DUETO HIGH TEMPERATURE CONDITIONS EXPERIENCED AS A RESULT OF SAID IN SITUCOMBUSTION, (4) COLLECTING THE RESULTING COOLED FORMATION FLUIDS WITHINSAID WELLBORE AT A LOCATION THEREIN REMOTE FROM SAID FORMATION, AND (5)TRANSFERRING THE RESULTING COOLED FORMATION FLUIDS FROM THE LASTMENTIONED LOCATION VIA SAID WELLBORE TO THE SURFACE.